1. Field of the Invention
The present invention relates to an improved heavy duty shackle having particular utility in the salvaging of underwater objets. More particularly, the present invention relates to an improved shackle having a shackle body that is generally u-shaped, a shackle pin that fits openings in the arms of the shackle and wherein a nut is permanently and rotatably attached to the shackle body on one of the arms, the pin being prevented from rotating with respect to the shackle body and wherein a connection of the pin to the nut is achieved by engaging correspondingly shaped threads of the pin and nut and by rotating the nut. When used in an underwater environment, the present invention prevents inadvertent loss of the nut or pin because they are both permanently attached to the body of the shackle.
2. General Background of the Invention
Shackles are commonly used as a part of rigging when lifting very heavy objects. Typically, a lift employs a lifting device such as a crane that has a lift line and a lifting hook. A number of slings can be attached to the crane lifting hook and then extending diagonally to various points of attachment on the load. When salvaging an underwater object such as sunken vessel, boat, ship or the like, divers are employed to attache rigging to selective locations on the vessel to be salvaged. In an underwater environment, it is easy for a diver to drop a part of the shackle rendering the entire apparatus useless.
Shackles that are employed in underwater salvage can be quite massive, having weights in the hundreds of pounds. Such shackles cannot be typically lifted by a diver in an underwater operation without some assistance.
Various shackle constructions have been patented. The following table lists examples of such patents that are directed to shackle constructions.
The following U.S. patents are incorporated herein by reference:
TABLEPATENT NO.TITLEISSUE DATE  417,417Nut-LockDec. 17, 18891,719,673ShackleJul. 02, 19292,449,593Jib Sheet ShackleSep. 21, 19482,909,386Shackle MeansOct. 20, 19593,958,411ShackleMay 25, 19764,079,584Heavy Duty ShackleMar. 21, 19784,273,371Claw Hook AssemblyJun. 16, 19814,690,167Fireplug Anti-Theft ApparatusSep. 01, 19875,046,881Lockable Pin and ClevisSep. 10, 1991Re.34,046Heavy Duty ShackleSep. 01, 19926,023,927Shackle with a Kant Loose PinFeb. 15, 20006,145,293Safety ShackleNov. 14, 2000Des.433,617Chain Shackle with PinNov. 14, 2000Locking Structure